Menopause is the physiological cessation of menstrual cycles associated with advancing age of females in species that experience such cycles. Menopause is sometimes referred to as change of life or climacteric.

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Menopause occurs as the ovaries stop producing estrogen, causing the reproductive system to gradually shut down. As the body adapts to the changing levels of natural hormones, vasomotor symptoms such as hot flashes and palpitations, psychological symptoms such as increased depression, anxiety, irritability, mood swings and lack of concentration, and atrophic symptoms such as vaginal dryness and urgency of urination appear. Together with these symptoms, the woman may also have increasingly scanty and erratic menstrual periods. The term menopause comes from the Greek roots 'meno-' (month) and 'pausis' (a pause, a cessation).

Technically, menopause refers to the cessation of menses; whereas the gradual process through which this occurs, which typically takes a year but may last as little as six months or more than five years, is known as climacteric. Very early symptoms that precede menopause, referred to as perimenopause, typically begin in the late 30s. Popular use replaces climacteric with menopause. A natural or physiological menopause is that which occurs as a part of a woman's normal aging process. However, menopause can be surgically induced by such procedures as hysterectomy (when this procedure includes oophorectomy, removal of the ovaries).

The average onset of menopause is 50.5 years, but some women enter menopause at a younger age, especially if they have had cancer or another serious illness and undergone chemotherapy. Premature menopause (or premature ovarian failure) is defined as menopause occurring before the age of 40, and occurs in 1% of women. Other causes of premature menopause include autoimmune disorders, thyroid disease, and diabetes mellitus. Premature menopause is diagnosed by measuring the levels of follicle stimulating hormone (FSH) and luteinizing hormone (LH); the levels of these hormones will be higher if menopause has occurred. Rates of premature menopause have been found to be significantly higher in both fraternal and identical twins; approximately 5% of twins reach menopause before the age of 40. The reasons for this are not completely understood. Transplants of ovarian tissue between identical twins have been successful in restoring fertility.

Post-menopausal women, especially Caucasian women of European descent, are at increased risk of osteoporosis. One for this risk is the dramatic change in female sex hormone levels that occurs: These hormones play a major role in female skeletal development and changes lead to an acceleration of bone mass loss rate.

Unlike in humans, animals rarely experience menopause. This may simply be due to animals short lifespans. However, recent studies have shown menopause in gorillas, with an average age of 44 at onset.
The Grandmother hypothesis considers that the menopause arose in human evolution, because later life infertility could actually confer an evolutionary advantage. This acts through the diversion of a woman's care from any additional new offspring of her own, to care for the woman's genes present in her existing children and grandchildren.

Perimenopause refers to the time preceding menopause, during which the production of hormones such as estrogen and progesterone diminishes and becomes more irregular. During this period fertility diminishes, menopause is arbitrarily defined as a minimum of twelve months without menstruation. Symptoms of perimenopause can begin as early as age 35, although most women become aware of them much later. It can last for a few months or for several years. The duration of perimenopause cannot be predicted in advance.

The cessation of menses is the result of the eventual atresia of almost all oocytes in the ovaries. This causes an increase in circulating FSH and LH levels as there are a decreased number of oocytes responding to these hormones and producing estrogen. This decrease in the production of estrogen leads to the post-menopausal symptoms of hot flashes, insomnia, osteoporosis, atherosclerosis, vaginal atrophy and depression.

Cigarette smoking has been found to decrease the age at menopause by as much as one year. However, premature menopause (before the age of 40) is generally idiopathic.

While menopause is a natural stage of life, some symptoms may be alleviated through medical treatments. Hormone Replacement Therapy (HRT) provides the best relief, but certain forms appear to pose very significant health risks. Some drugs afford limited relief from hot flashes. A woman and her doctor should carefully review her symptoms and relative risk before determining whether the benefits of HRT or other therapies outweigh the risks. Until more becomes known, women who elect to use hormone replacement therapy are generally well advised to take the lowest effective dose of HRT for the shortest period of time possible, and to investigate whether certain forms may pose fewer dangers of clots or cancer than others.

In addition to relief from hot flashes, Hormone Replacement Therapy (HRT), remains an effective treatment for osteoporosis. Women had also been advised for many years that hormone therapy after menopause might reduce their risk of heart disease and various aspects of aging. However, a large, randomized, controlled trial (the Women's Health Initiative) found that women undergoing HRT with equine estrogens, with and without combination with progestins (Premarin or PremPro) had an increased risk of breast cancer sufficient to justify stopping the study, and also suffered from increased risks of heart disease, stroke, and even Alzheimer's disease. After these results were reported in 2002, the number of prescriptions written for Premarin and PremPro in the United States dropped almost in half, as women discontinued HRT altogether or switched to bioidentical hormone replacement therapy (which does not appear to present the same health risks as Premarin or PremPro). The sharp drop in prescriptions for Premarin and PremPro following the mid-2002 announcement of their dangers was followed by large and successively greater drops in new breast cancer diagnosis at six months, one year, and 18 months after that announcement, for a cumulative 15% drop by the end of the following year (2003). Surprisingly, no similar drop in Canada's lower breast cancer rates was observed during the same period, though prescriptions of PremPro and Premarin were reduced in Canada as well. Studies designed to track the further progression of this trend after 2003 are underway.

The anti-seizure medication gabapentin (Neurontin) seems to be second only to HRT relieving hot flashes.

Antidepressants such as paroxetine (Paxil), Fluoxetine hydrochloride (Prozac), and Venlafaxine hydrochloride (Effexor) have been used with some success in the treatment of hot flashes, improving sleep, mood, and quality of life. Of these, Paxil has been the most studied and may provide the most consistent relief. There is theoretical reason that SSRI antidepressants might help with memory problems by increasing circulating serotonin in the brain and restoring hippocampal function. Prozac has been repackaged as Femara and is approved and prescribed for Pre-menstrual distress syndrome (PMDD), a mood disorder often exacerbated during perimenopause and early menopause. PMDD has been found by PET scans to be accompanied by a sharp drop in Serotonin in the brain and to respond quickly and powerfully to SSRIs.

About as effective as antidepressants for hot flashes, but without other mind and mood benefits of antidepressants, are blood pressure medicines including clonidine (Catapres). These drugs may merit special consideration by women suffering both from high blood pressure and hot flashes.

It should be noted that medical non-hormone treatments provide less than complete relief, and each has side effects.

In the area of complementary and alternative therapies, some studies have noted a slight benefit from soy isoflavones. Other remedies that have proven no better than a placebo at treating hot flashes and other menopause symptoms include red clover isoflavone extracts and black cohosh. Black cohosh has potentially serious side-effects such as the stimulation of breast cancer, therefore prolonged administration is not recommended in any case.

Obvious measures, such as drinking cold liquids and removing excess clothing layers when hot flashes strike, and avoiding hot flash triggers such as spicy foods, may supplement or supplant the use of medications for some women.